1. Field of the Invention
The invention relates to a belt and chain drive for vehicles or for use in drive technology with an input shaft and an output shaft supported on a frame, the input shaft and the output shaft projecting out of the frame, with the following features:                a) Gear transmissions with gear wheels, which are embodied belt and chain drives, are located between the input shaft and the output shaft,        b) All of the gear wheels are constantly in rotation during operation,        c) The gear transmissions located between the input shaft and the output shaft are embodied as belt and chain drives with toothed belts as traction means and with pulleys as gear wheels,        d) The traction means are reinforced with aramide, Kevlar, carbon fibers or other fibrous materials.        
2. Discussion of Background Information and Invention
The field of motorized vehicles has been unimaginable without manual transmissions for the past 100 years. They are also used in numerous machines in drive technology. These are very often gear constructions that work with the aid of gear wheels as spur gear transmissions or epicyclic gearing (planetary transmissions). However, the production engineering of these transmissions is generally very complex and expensive. Since these power-transmitting transmission components are generally made from steel, weight is increasingly the focus of criticism at the moment and should be considered a disadvantage. Lighter transmissions would reduce energy consumption, for example. The invention described below can be used in all conceivable product branches and is excellently suitable for use in vehicles particularly with respect to the low weight, since fiber-reinforced plastics are used as power-transmitting components. Ground vehicles, aircraft and watercraft, which can be equipped with internal combustion engines, electric motors or also other units, are to be considered by way of example here. Use is also conceivable in human powered vehicles. In order to ensure easy propulsion, the vehicles must be extraordinarily light. The functional description of the transmission is to be provided based on the example of a bicycle for this reason.
Over the past forty years, the chain drive with a shifting method on the rear axle has gained acceptance in bicycles. To this end, a rotatable bottom bracket with one or several chain wheels is mounted on the frame, which forms the load-bearing component of the bicycle with all of its mounting points for the front fork, the seat post and the rear wheel. A cassette comprising up to ten pinion gears of different sizes is located on the hub of the rear wheel. A derailleur is mounted on a fork end, which is located directly on the rear axle, the function of which derailleur is to guide the chain on the pinion gears of the cassette and to make it possible to shift gears. Through a front derailleur located generally on the seat tube it is possible to change between the different chain wheels on the bottom bracket.
Due to the shifting capability, the rider can adapt the transmission of his drive to the respective riding situation. Bicycles with a shifting system as described above are generally referred to as bicycles with derailleur gears.
Since the components are mounted outside on the frame for structural reasons in the case of a bicycle with derailleur gears, they are exposed to environmental influences to a particularly high degree. For example, dirt and water reach the derailleur, chain, cassette and other components unhindered. This means that the initially very high efficiency of a derailleur gear is drastically reduced, so that a substantial part of the force has to be expended to overcome the resistances inside the transmission. In order to guarantee the function it is necessary for the components of the derailleur gear to be regularly maintained; this includes cleaning and oiling the components as well as meticulous adjustment. This can be easily changed, for example, during collisions or contact with objects (stones, branches, etc.). Since even with the most intensive maintenance the smallest dirt particles are retained in the transmission and in particular in the bearings, some parts have to be regularly replaced. In particular the parts subject to wear, such as chain wheels and chain, call for annual replacement, which is again associated with additional expense.
Shifting in the derailleur gear is possible only when the pinion gears are rotating, since otherwise the chain cannot be changed. It must therefore be considered to be a further disadvantage that shifting at a standstill is impossible due to the structural design.
Furthermore, components can be damaged or torn off the frame during a collision or by contact with stones or branches. The listed circumstances have to be considered to be a disadvantage of derailleur gears.
As an alternative to “derailleur gear” the so-called “integral rear hub” was developed in which the shifting takes place in a transmission in the rear wheel hub. The parts derailleur, front derailleur and cassette, which are required with a derailleur gear are thus omitted. Bicycles of this type are generally referred to as bicycles with integral rear hub. An integral rear hub thus avoids the disadvantages of a derailleur gear. However, the weight of the rear wheel is increased due to the transmission integrated into the rear wheel hub. An increase in the mass on the rear wheel is very noticeable in particular in the case of so-called mountain bikes, which are ridden off-road. This applies above all to those with rear wheel suspension. The ratio of sprung to unsprung mass is of decisive importance for the riding behavior of a sprung wheel. The greater the unsprung mass in relation to the sprung mass, the more critical the riding behavior of the wheel. Impacts caused by unevenness in the road surface cannot be optimally absorbed by the chassis with high unsprung mass (heavy rear wheel).
With a known bicycle (cf. DE 103 39 207) the transmission is located inside the bicycle frame. The bottom bracket housing of the classic bicycle frame is omitted and is replaced by the gear housing. This is a common housing for gears and bottom bracket. Similar to bicycles with speed hub, the force with gearwheels is transferred via a chain or a toothed belt to the rear wheel. The chain and the rear hub do not have a shifting function in this system. The rear hub can thus be constructed to be very light, which results in a more effective rear wheel suspension. In addition, the center of gravity is located in the center of the wheel, directly under the rider. A more agile and controlled riding behavior is the result. Furthermore, the so-called “platform strategy” can be used with the aid of the transmission integrated in the frame. It has hitherto been usual in bicycle design to first construct a frame and then to equip it with the components afterwards, but now with the concept of the transmission integrated in the frame it is possible for the first time to use the platform strategy from car manufacturing in bicycle production. For example, components such as gearshift, suspension, the entire drive train as well as brakes, generator and lighting can be firmly attached in the gear housing as a platform. The customer-specific parts that complete the bicycle according to the customer or manufacturer requirements are then mounted on the transmission thus equipped. The transmission according to DE 103 39 207 comprises a planetary transmission and a primary drive. The primary drive is necessary because the planetary transmission developed for use in a speed hub cannot withstand the high moments acting in the bottom bracket. The planetary transmission is brought to a higher speed by the primary drive in order to withstand the acting forces. However, the efficiency of the drive is reduced due to this construction. This must be considered a disadvantage compared to the invention. Similar transmissions are likewise known, for example, from: U.S. Pat. Nos. 5,553,510, 4,955,247, 5,924,950, DE 20 201 787 U1, WO 2006/039880 A1, US 2004/0067804 A1 and US 2004/0066017 A1. Their structure is generally very heavy and complex. The invention provides a light and very simply structured solution for the referenced transmission type. All of these transmissions produce different speed changes between two parallel shafts. Usually one of the shafts is the drive shaft and another shaft is the driven shaft hereby. The drive shaft is also referred to below as the input shaft. The driven shaft is also referred to below as the output shaft. Wherever just the term shaft is used below, this means the input or the output shaft.
The invention thus improves multiple gears with input shaft and output shaft, wherein the input shaft is embodied to absorb the input torque and the output shaft generally projects from the gear housing and is embodied at this end to transfer the torque to the wheels of the vehicle. For example, belt wheels are mounted parallel on the input shaft and the output shaft in the housing and connected in pairs to traction means. With the aid of a gear mechanism, the belt wheels can be coupled to the output shaft. The vehicle can be a bicycle, for example, wherein the input shaft is embodied there to receive cranks and projects at both ends from the gear housing. The output shaft has on its end a pinion gear for torque transmission to the rear wheel. The vehicle can also be a motorcycle, in which the transmission is advantageously located behind the crankcase. The input shaft is connected to the crankshaft in a suitable manner. The output shaft transmits the torque through a further machine element (for example, chain, toothed belt, cardan) to the rear wheel. Use in a motor vehicle in an advantageous manner is also conceivable.
A belt and chain drive of this type is known, for example, from U.S. Pat. No. 4,158,318. In the case of this transmission, several sprockets with different diameters are rotatably mounted on the axle. The sprockets can be connected to the shaft by a coupling in a rotatably fixed manner and thus transmit a torque. The disadvantage of this invention lies on the one hand in the high weight, in particular through the use of a steel chain, on the other hand in the large space needed, the complexity of the couplings and the coupling selector.
A similar belt and chain drive is known, for example, from US 2004/0067804 A1 and US 2004/0066017 A1. With these bicycle transmissions different belt wheels are mounted on the drive shaft and the driven shaft, which are connected in pairs to traction means. Different speed ratios are achieved in that a shifting component is axially displaced inside the driven shaft with the aid of a cable. A connection element on the shifting component couples into the desired belt wheel and produces a rotationally fixed connection between driven shaft and belt wheel. However, the design described has disadvantages, which are explained in more detail below.
Both patents disclose in their main claim that the belt wheels are integrated next to one another such that they form the shape of a conical envelope. The shape of a conical envelope is formed when the diameter of the belt wheels increases from small to large on the shaft. It is precisely this peculiarity of US 2004/0067804 A1 and US 2004/0066017 A1 that is to be considered a disadvantage:
Transmissions on bicycles should increase speed in the range of 0.7-4.0. If the size of the chain wheels and their number of teeth is considered in US 2004/0067804 A1 and US 2004/0066017 A1, this speed change range can be achieved only with difficulty compared to the invention. Furthermore, when considered in terms of sports biology, only gear transitions that account for less than 15% can be handled well by the human organism.
The so-called secondary transmission is formed by two further belt wheels, which transmit the torque from the gears to the rear wheel. It is advantageous if these belt wheels do not through their proportions impair the function of the cranks and the rear wheel hub. The design according to US 2004/0067804 A1 and US 2004/0066017 A1 would be very large and voluminous in construction if the basic conditions in terms of secondary transmission, total transmission and gear transition are to be achieved. The invention is much smaller in construction compared to the cited structures.
Belt and chain drives generally have a discrete axial distance, which depends exclusively on the pitch and the length of the traction means and the diameter or number of teeth of the belt wheels used.
This axial distance can be described by the following formula:
  a  =      p    /          4      [              X        -                  (                                    z              1                        +                                          z                2                            /              2                        +                                          [                                  X                  -                                                            (                                                                        z                          1                                                +                                                                              z                            2                                                    /                          2                                                                    ]                                        2                                    -                                                            8                      ⁡                                              [                                                                              (                                                                                          z                                2                                                            -                                                              z                                1                                                                                      )                                                    /                                                      (                                                          2                              ⁢                              π                                                        )                                                                          ]                                                              2                                                                                ]                        a=axial distance    p=chain pitch of the chain    X=number of links in the chain    z1=number of teeth of the small chain wheel    z2=number of teeth of the large chain wheel
If this formula is applied to US 2004/0067804 A1 and US 2004/0066017 A1, it is found that not each individual belt wheel has the correct axial distance. A design according to US 2004/0067804 A1 and US 2004/0066017 A1 is thus disadvantageous, since some chains are taut and others are too loose. This must be considered a major disadvantage compared to the invention, since incorrectly tensioned traction means have too high a wear.
This advantage is described below as “only discrete axial distances possible.” Also in U.S. Pat. No. 4,158,316 only discrete axial distances are possible due to the traction means used. This must also be considered as a disadvantage. In addition, it should be noted that this disadvantage of discrete axial distances also applies to gear trains.
Another major disadvantage can be found in U.S. Pat. No. 4,158,316, US 2004/0067804 A1 and US 2004/066017 A1 inside the gear mechanism. If a gear change is to be performed, first a belt wheel is uncoupled from the driven shaft and only thereafter is a further belt wheel coupled into the shaft. The result is that with these drives a constant rotationally fixed connection between the shaft and a gear wheel is not ensured. A neutral position can occur during a gear change. For the cyclist this means suddenly “pedaling into nothing.” Injuries, particularly in the knee area, can thus occur. The invention is structured such that idling cannot occur between the individual gears during the gear change. This must be considered a major advantage.
In the past, belt and chain drives with traction means running in a parallel manner have repeatedly been encountered in which the belt wheels are coupled into an axle (see also CH 167367, U.S. Pat. No. 6,146,296 and U.S. Pat. No. 5,871,412). However, all of these constructions have the disadvantage that a small time window with an idle could occur between two coupled-in speed changes. In particular under load it cannot be ensured that during this time window a short belt slip could occur. Likewise, a belt slip of this type leads to enormous wear on the couplings. In the long term, damage cannot be ruled out under some circumstances. The invention has the advantage that a torque-transmitting component is always engaged between two gears during the gear change.
In summary, many transmissions according to the prior art have problems with respect to weight, production costs, shifting capability under load, idling and shifting capability at a standstill.